Blueberry named ‘Robeson’

ABSTRACT

Vaccinium ×‘Robeson’ is a new and distinct pentaploid variety of blueberry plant that has the following unique combination of desirable features that are outstanding in a new variety.
         1. A ripening season that bridges the gap between highbush and rabbiteye blueberry varieties.   2. Consistent yields of medium size fruit best suited for local direct marketing.   3. Very good fruit quality and good color.   4. Very vigorous plants with upright plant habit and broad soil adaptation, including higher pH soils.

Latin name of the genus and species: The Latin name of the novelblueberry plant variety disclosed herein is Vaccinium×‘Robeson’.

Variety denomination: The inventive hybrid Vaccinium plant cultivardisclosed herein is pentaploid with 2n=5X=60 chromosomes and has beengiven the variety denomination ‘Robeson’.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct pentaploid hybridVaccinium (blueberry plant) cultivar grown as a fruiting woody shrub forcommercial agriculture. Blueberries are typically consumed both freshand in a number of processed products.

The new and distinct pentaploid hybrid variety of blueberry (VacciniumLinnaeus) plant originated from the hand pollinated cross of ‘US 226’[tetraploid (2n=4x=48 chromosomes), a hybrid of Vaccinium corymbosumLinnaeus×V. myrtilloides Michaux] (unpatented)×‘Premier’{hexaploid(2n=6X=72 chromosomes) [(V. virgatum Aiton (syn. V. ashei Reade)]}(unpatented) made in 1980 in Raleigh, N.C. ‘US 226’ was an earlyblooming and early ripening genotype that produced medium size andrather soft light blue fruit during highbush blueberry (V. corymbosumL.) ripening season on a plant that was highly resistant to phytophthoraroot rot caused by Phytophthora cinnamoni. ‘Premier’ is the standardearly ripening rabbiteye blueberry (V. virgatum Ait.) cultivar growncommercially in North Carolina. (Early ripening rabbiteye cultivarsstart ripening about four weeks after early ripening highbushcultivars.) ‘Premier’ also blooms early and produces large size highquality light blue fruit that is medium in fruit firmness on a veryvigorous plant that is resistant to phytophthora root rot.

Seeds from this hand pollination were germinated in winter 1980/1981 inRaleigh, N.C., and 35 seedlings were established at Jackson Springs,N.C., in 1982. When the seedlings reached maturity in 1986, an elitegenotype designated as ‘NC 2849’ was selected for its vigorous erectplant habit, productivity, fruit size, color, picking scar, firmness,quality and early maturity by James R. Ballington. ‘NC 2849’ was by farthe superior genotype of the two seedlings in the progeny of 35 thatproduced attractive blue fruit.

During 1987 the original seedling of ‘NC 2849’ was propagated byhardwood stem cuttings in Raleigh, N.C., and following rooting, singlethree plant plots were established at Jackson Springs and Fletcher, N.C.in 1988. Based on its performance in these initial trials, in 1996 itwas propagated by softwood stem cuttings and established in a replicatedtrial at Castle Hayne, N.C. It was also established in a grower trial atIvanhoe, N.C., under a Memorandum of Agreement whereby the growerprovided the land and care of the plants and North Carolina StateUniversity retained ownership of the variety. Plants and fruit of thisnew variety have remained true to type through these successive cyclesof asexual propagation. This new variety has been named the ‘Robeson’cultivar.

SUMMARY OF THE INVENTION

‘Robeson’ is a new and distinctive pentaploid blueberry plant thatdiffers from its female parent, ‘US 226’, for leaf and stem pubescenceand leaf margins. The stems and abaxial surfaces of the leaves of ‘US226’ were densely pubescent and the leaf margin entire. The stems andleaves of ‘Robeson’ were glabrous and the apical ⅔ of the leaf marginsserrulate. ‘Robeson’ differed from its male parent, ‘Premier’, forinternode length of first flush growth, number of renewal stems, dormantstem color on the unexposed stem surface, first flush stem color insummer, presence of leaf glands, fruit shape and number of seeds perberry. ‘Premier’ had a first flush internode length of 18 cm compared to11 cm for ‘Robeson’. ‘Premier’ had three renewal stems per plant and‘Robeson’ one. The dormant stem color on the unexposed surface was greenfor ‘Premier’ and yellow-green for ‘Robeson’. The first flush summerstem color of ‘Premier’ was yellow-green and green for ‘Robeson’. Theabaxial leaf surface of leaves of ‘Premier’ have sparse stalked glandsalong lateral veins while the leaves of ‘Robeson’ were eglandular.‘Robeson’ had only about ⅓ the number of seeds per berry as ‘Premier’.

‘Robeson’ begins ripening somewhat earlier than its ‘Premier’ parent,and bridges the gap between late ripening highbush blueberry cultivarsand early ripening rabbiteye blueberry cultivars. The plant is veryvigorous and upright with very broad soil adaptation, including higherpH soils. Yield is good and similar to Premier. Fruit size was mediumand similar to ‘Tifblue’. Firmness was only average and similar to‘Premier’, so that it was not adaptable to mechanical harvesting for thefresh market. Fruit color was equal to ‘Premier’ based on the R.H.S.color chart, but not quite as good based on Minolta Color Meterdeterminations. Fruit quality ratings for ‘Robeson’ showed it to besuperior to ‘Premier’ and equal to ‘Tifblue’, but not quite equal to‘Columbus’. Short shelf-life of fruit indicated that it was best suitedfor local direct marketing outlets. Leaves were narrowlyelliptic-obovate in shape and both the leaf base and apex angles acute.The flowers were not self-fertile and produced very little viablepollen. The corolla of individual flowers was white andcylindro-urceolate in shape. The fruit was round-oblate in shape and thecalyx not prominent and appressed to the apex of the fruit. ‘Robeson’ isreadily asexually propagated by either softwood or hardwood stemcuttings and has remained true to type through successive generations ofasexual propagation. The chilling requirement of dormant buds on‘Robeson’ plants is 400 to 600 hours below 45° F. It is susceptible tostem canker, but has not had any problems to date with stem blight. Itis resistant to phytophthora root rot.

BRIEF DESCRIPTION OF THE DRAWINGS

The photographs in the drawings were made using digital photographytechniques, and illustrates the colors as true as reasonably possiblewhen using these techniques. Colors in the photographs may differslightly from the color values cited in the detailed botanicaldescription, which accurately describe the colors of the new pentaploidhybrid Vaccinium plant variety. All photographs were taken from nineyear old plants growing at Castle Hayne, N.C.

FIG. 1 shows the typical plant habit of ‘Robeson’.

FIG. 2 shows the typical fruit of ‘Robeson’.

DETAILED BOTANICAL DESCRIPTION OF THE VARIETY

The following is a detailed botanical description of a new and distinctpentaploid hybrid variety of Vaccinium Linnaeus plant known as‘Robeson’. The observations below are from mature plants grown in testplots at a standard commercial spacing of 4′ between plants in rows and10′ between rows, at Castle Hayne, N.C. Those skilled in the art ofcultivar description and evaluation will appreciate that certaincharacteristics of a variety will vary with older or, conversely, withyounger plants. ‘Robeson’ has not been observed under all possibleenvironmental conditions. Where dimensions, sizes, colors and othercharacteristics are given, it is to be understood that suchcharacteristics are approximations or averages set forth as accuratelyas practicable. The phenotype of the variety may differ from thedescriptions herein with variations in the environment such as season,temperature, light intensity, day length and cultural conditions. Colornotations are based on The Royal Horticultural Society Colour Chart, TheRoyal Horticultural Society, London, UK, 1995 edition.

For botanical description purposes, ‘Robeson’ was compared to its‘Premier’ parent. The botanical descriptive data presented are averagesof data collected from mature nine year old plants growing in areplicated trial at Castle Hayne, N.C., in 2005. The exception to usingaverage values was with seed numbers where these were determined from arepresentative fruit of each cultivar.

-   Plant:    -   -   Dimensions.—‘Robeson’ — 1.6 m height, 1.4 m diameter, H/D            ratio 1.14. ‘Premier’ — 1.9 m height, 1.5 m diameter, H/D            ratio 1.27.        -   Growth habit.—Upright for ‘Robeson’ (FIG. 1) and ‘Premier’.        -   Vigor.—Very good for ‘Robeson’ and ‘Premier’.        -   Plant adaptation.—‘Robeson’ and ‘Premier’ are both very            broadly adapted to soils including higher pH soils.        -   Mature cane diameter.—4.4 cm for ‘Robeson’ and ‘Premier’.        -   Mature cane length.—‘Robeson’ — 1.1 m. ‘Premier’ — 1.5 m.        -   Internode length on first flush growth.—‘Robeson’ — 11.0 cm.            ‘Premier’ — 18.0 cm.        -   Number of renewal stems.—‘Robeson’ — 1.0. ‘Premier’ — 3.0.        -   Dormant mature stem color.—Grayed-green (RHS 198D) for            ‘Robeson’ and ‘Premier’.        -   Dormant one year stem color.—‘Robeson’ — red (RHS 53B) on            the exposed surface, yellow-green (RHS 148B) on the            unexposed surface. ‘Premier’ — red (RHS 53B) on the exposed            surface, green (RHS 137D) on the unexposed surface.        -   First flush growth stem color in summer.—‘Robeson’ — green            (RHS 138C). ‘Premier’ — yellow-green (RHS 147C).        -   Pubescence on summer and one year dormant stems.—No stem            pubescence on ‘Robeson’ or ‘Premier’.-   Leaves:    -   -   Leaf blade dimensions.—‘Robeson’ — length 81 mm, width 41            mm, L/W ratio 1.98. ‘Premier’ — length 81 mm, width 34 mm,            L/W ratio 2.38.        -   Leaf petiole length.—‘Robeson’ — 4 mm. ‘Premier’ — 3 mm.        -   Leaf shape.—‘Robeson’ — narrowly elliptic-obovate. ‘Premier’            — narrowly elliptic-obovate to oblanceolate.        -   Leaf apex angle.—‘Robeson’ — acuminate to acute. ‘Premier’ —            acuminate.        -   Leaf base angle.—Acute for ‘Robeson’ and ‘Premier’.        -   Leaf margin.—‘Robeson’ — apical ⅔ serrulate. ‘Premier’ —            serrulate.        -   Leaf pubescence.—None for Robeson and Premier.        -   Leaf glands.—‘Robeson’ — none. ‘Premier’ — sparse stalked            glands along lateral veins on the abaxial surface.        -   Leaf color.—The adaxial surface color is green (RHS 137A)            and the abaxial color green (RHS 138B) for ‘Robeson’ and            ‘Premier’.-   Flowers:    -   -   Number of petals.—Five, fused into a corolla tube for            ‘Robeson’ and ‘Premier’.        -   Number of flowers per inflorescence.—‘Robeson’ — 4.0.            ‘Premier’ — 4.0.        -   Flower dimensions.—‘Robeson’ — length 9.0 mm, diameter 5.0            mm, L/D ratio 1.8. ‘Premier’ — length 9.0 mm, diameter 4.0            mm, L/D ratio 2.2.        -   Length of the single style.—‘Robeson’ and ‘Premier’ — 8.0            mm.        -   Flower shape.—‘Robeson’ — cylindro-urceolate. ‘Premier’ —            cylindraceous to cylindro-urceolate.        -   Flower color.—‘Robeson’ — red-purple (RHS 63B) on the basal            half and mainly on the petal lobes just prior to opening,            fading to white (RHS 155C) when fully open. ‘Premier’ —            red-purple (RHS 63D) just prior to opening, fading to white            (RHS 155C) on fully open flowers.-   Fruit:    -   -   Fruit dimensions.—‘Robeson’ — length 15 mm, diameter 17 mm,            L/D ratio 0.88. ‘Premier’ — length 15 mm, diameter 18 mm,            L/D ratio 0.83.        -   Fruit shape.—‘Robeson’ — round-oblate. ‘Premier’ — oblate.        -   Fruit pedicel length.—‘Robeson’ and ‘Premier’ — 8 mm.        -   Fruit picking scar.—‘Robeson’ — 2.0 mm diameter, dry.            ‘Premier’ — 1.0 mm diameter, dry.        -   Fruit calyx orientation and prominence.—Appressed against            the apical end of the fruit and not prominent for ‘Robeson’            And ‘Premier’.        -   Fruit color with bloom (epicuticular wax).—‘Robeson’            (FIG. 2) and ‘Premier’ — violet-blue (RHS 97B).        -   Fruit color without bloom.—Black (RHS 202A) for ‘Robeson’            and ‘Premier’.-   Seeds:    -   -   Number of fully developed seeds per berry.—‘Robeson’ — 14.            ‘Premier’ — 46.        -   Seed dimensions.—‘Robeson’ — length 1.50 mm, width 1.00 mm,            L/W ratio 1.5. ‘Premier’ — length 2.00 mm, width 1.00 mm,            L/W ratio 2.0.        -   Seed shape.—Basically depressed-ovate for ‘Robeson’ and            ‘Premier’.

For technical (pomological) descriptive data purposes ‘Robeson’ wascompared to ‘Premier’, ‘Columbus’ (unpatented) and ‘Tifblue’(unpatented) at Castle Hayne, N.C., in Tables 2-7. The exception was fortime of flowering, where the data was more representative from JacksonSprings, N.C., in 1992, and compared ‘Robeson’ with ‘Premier’ and‘Tifblue’ (Table 1).

-   Time of flowering: ‘Robeson’ was a few days later than ‘Premier’ for    date of first bloom and a few days later for date of 50% bloom    (Table 1). It was just over a week earlier than ‘Tifblue’ for both    first bloom and 50% bloom.

TABLE 1 Time of flowering of blueberry cultivars at Jackson Springs, NC.1992. Cultivar Date of first bloom Date of 50% bloom Robeson 3/23 4/11Premier 3/21 4/14 Tifblue 4/1 4/20

-   Pollination requirements: The flowers of ‘Robeson’ are not    self-fertile and require cross-pollination to set commercial crops    of fruit. ‘Premier’ has a bloom pattern similar to ‘Robeson’ and has    proved to be an excellent pollinator for this variety.-   Pollen production: ‘Robeson’ flowers produce very little viable    pollen since the variety is pentaploid.-   Season of ripening: ‘Robeson’ was somewhat earlier ripening than    ‘Premier’ and much earlier ripening than either ‘Columbus’ and    ‘Tifblue’ (Table 2).

TABLE 2 Season of ripening for blueberry cultivars at Castle Hayne, NC.Cumulative percent ripe by June 29th¹ Cultivar 1999 2000 2001 AverageRobeson 100 100 100 100 Premier 86 100 93 93 Columbus 40 57 33 43Tifblue 42 0 0 14 ¹Percent ripe after the first two weeks of the season.

-   Yield per plant: In 1999 and 2001 there were no significant    differences between ‘Robeson’ and the other three varieties for    yield, and yield was quite good for all four in 2001 (Table 3).    Yield in 2000 was adversely affected by the harvest method (rubber    hoses) due to excessive fruit falling to the ground, so the    significant differences indicated were not meaningful.

TABLE 3 Yield of blueberry cultivars at Castle Hayne, NC. Yield(lbs./plant)¹ Cultivar 1999 2000² 2001 Robeson 4.6 3.1bc 15.2 Premier6.6 4.8b 15.8 Columbus 5.5 11.2a 19.8 Tifblue 6.8 9.0a 18.3 ¹Values notfollowed by the same letter(s) are significantly different at the 0.05level (Duncan's Multiple Range Test). ²Yield adversely affected byharvest method (catch frames and rubber hoses).

-   Fruit size (weight per berry): Fruit size of ‘Robeson’ was equal to    ‘Tifblue’ two years out of three, and ‘Premier’ one year out of    three (Table 4). It had the smallest average size of the four    varieties. ‘Robeson’ therefore has medium size fruit suitable for    mechanical harvesting.

TABLE 4 Fruit size of blueberry cultivars at Castle Hayne, NC. Fruitsize (weight per berry in grams)¹ Cultivar 1999 2000 2001 AverageRobeson 1.13c 1.46bc 1.35c 1.31 Premier 1.72b 1.56b 1.78b 1.69 Columbus2.07a 2.08a 2.12a 2.09 Tifblue 1.64b 1.41c 1.36c 1.47 ¹Values notfollowed by the same letter(s) are significantly different at the 0.05level (Duncan's Multiple Range Test).

-   Fruit color: In addition to The Royal Horticultural Society Colour    Chart, fruit color was also determined objectively with a Minolta    Color Meter (Table 5), and these data indicated that ‘Robeson’ was    equal to ‘Tifblue’ for color, but not to equal to ‘Premier’ or    ‘Columbus’ by this means of comparison.

TABLE 5 Fruit color and fruit firmness of blueberry cultivars at CastleHayne, NC. Color^(1,2) Firmness^(1,3) Cultivar 2001 1999 2001 Robeson17.8c 98b   115c Premier 20.7b 104ab 133b Columbus 23.4a 102ab 137bTifblue 19.9bc 115a  175a ¹Values not followed by the same letter(s) aresignificantly different at the 0.05 level (Duncan's Multiple RangeTest). ²Color (lightness or “L” values) determined objectively by aMinolta Color Meter. Higher values indicate lighter blue color. ³Fruitfirmness determined objectively using a Firm-tech Firmness Tester.

-   Fruit firmness: Fruit firmness determined by a Firm-tech Firmness    Tester demonstrated that ‘Robeson’ was equal to ‘Premier’ and    ‘Columbus’ in 1999 (Table 5), but it was significantly less firm    than the other three varieties in 2001. Therefore, even though fruit    size of ‘Robeson’ is in the appropriate range for mechanical    harvest, the fruit is not sufficiently firm to mechanically harvest    for the fresh market, and would only be appropriate for processing    markets following mechanical harvesting.-   Fruit flavor: Subjective ratings for flavor indicated that ‘Robeson’    consistently scored in the very good range (Table 6), and fruit    quality is definitely one of this variety's strong points. It was    significantly better than ‘Premier’ in all three years, and equal to    or better than ‘Tifblue’ all three years. It was only equal to    ‘Columbus’ one year out of three.

TABLE 6 Fruit flavor of blueberry cultivars at Castle Hayne, NC.Flavor^(1,2) Cultivar 1999 2000 2001 Robeson 79a 77bc 78b Premier 75c75d   77c Columbus 79a 79a  80a Tifblue 77b 77bc 78b ¹Values notfollowed by the same letter(s) are significantly different at the 0.05level (Duncan's Multiple Range Test). ²Subjective ratings based on a0-90 scale, where less than 60 is unsatisfactory, 60-69 is satisfactory,70-79 is average to good, and 80 and above superior.

-   Post harvest shelf-life: Post harvest shelf-life of fruit is not one    of the strongest characteristics of ‘Robeson’ (Table 7). It was    significantly poorer than the other three varieties following seven    days storage at both temperatures. Therefore it is most strongly    recommended for production for local direct markets.

TABLE 7 Post harvest shelf-life of the fruit of blueberry cultivars atCastle Hayne, NC. in 2001. Percent marketable fruit after seven days¹Cultivar 50° F. 70° F. Robeson 46c 10c Premier 70b 25b Columbus 84a 69aTifblue 81a 77a ¹Values not followed by the same letter(s) aresignificantly different at the 0.05 level (Duncan's Multiple RangeTest).

-   Propagation: ‘Robeson’ is easily propagated asexually by both    hardwood and softwood stem cuttings.-   Chilling requirement: The chilling requirement of dormant leaf and    flower buds on ‘Robeson’ plants is 400 to 600 hours below 45° F.-   Disease reaction: ‘Robeson’ has not had any problems with stem    blight (Botryospaeria dothidea) one of the two major diseases    affecting blueberries in North Carolina. It is susceptible to the    other major disease, stem canker (Botryosphaeria corticis). It is    also resistant to phytophthora root rot (Phytophthora cinnamoni).

1. A new and distinct variety of commercial blueberry plant(Vaccinium×‘Robeson’) substantially as illustrated and described,characterized by its broad soil adaptation, early ripening, high yields,very good fruit quality, medium fruit size, limited numbers of seeds perfruit, and adaptation to direct market outlets.